Insulation compositions containing metallocene polymers

ABSTRACT

Novel additive systems for metallocene based filled cable insulation are disclosed. These systems provide excellent protection against thermal degradation, better cure state and reduced dissipation factor after prolonged heat exposure. The additives may contain one or more hindered amine light stabilizers and amine antioxidants.

FIELD OF THE INVENTION

The invention relates to insulation compositions for electric powercables having a base polymer comprising at least one metallocenepolymer, a filler; and an additive comprising a blend of (i) an amineantioxidant and (ii) at least one hindered amine light stabilizer, or2,5-Di(tert-amyl)hydroquinone (TAHQ), or mixtures of said stabilizer(s)and TAHQ.

BACKGROUND OF THE INVENTION

Typical power cables generally have one or more conductors in a corethat is surrounded by several layers that can include: a first polymericsemiconducting shield layer, a polymeric insulating layer, a secondpolymeric semiconducting shield layer, a metallic tape shield and apolymeric jacket.

Polymeric materials have been utilized in the past as electricalinsulating and semiconducting shield materials for power cables. Inservices or products requiring long-term performance of an electricalcable, such polymeric materials, in addition to having suitabledielectric properties, must be durable. For example, polymericinsulation utilized in building wire, electrical motor or machinerypower wires, or underground power transmitting cables, must be durablefor safety and economic necessities and practicalities.

One major type of failure that polymeric power cable insulation canundergo is the phenomenon known as treeing. Treeing generally progressesthrough a dielectric section under electrical stress so that, ifvisible, its path looks something like a tree. Treeing may occur andprogress slowly by periodic partial discharge. It may also occur slowlyin the presence of moisture without any partial discharge, with moistureand discharge, or it may occur rapidly as the result of an impulsevoltage. Trees may form at the site of a high electrical stress such ascontaminants or voids. in the body of the insulation-semiconductivescreen interface. In solid organic dielectrics, treeing is the mostlikely mechanism of electrical failures, which do not occurcatastrophically, but rather appear to be the result of a more lengthyprocess. In the past, extending the service life of polymeric insulationhas been achieved by modifying the polymeric materials by blending,grafting, or copolymerization of silane-based molecules or otheradditives so that either trees are initiated only at higher voltagesthan usual or grow more slowly once initiated.

There are two kinds of treeing known as electrical treeing and watertreeing. Electrical treeing results from internal electrical dischargesthat decompose the dielectric. High voltage impulses can produceelectrical trees. The damage, which results from the application ofmoderate alternating current voltages to the electrode/insulationinterfaces, which can contain imperfections, is commerciallysignificant. In this case, very high, localized stress gradients canexist and with sufficient time can lead to initiation and growth oftrees. An example of this is a high voltage power cable or connectorwith a rough interface between the conductor or conductor shield and theprimary insulator. The failure mechanism involves actual breakdown ofthe modular structure of the dielectric material, perhaps by electronbombardment. In the past much of the art has been concerned with theinhibition of electrical trees.

In contrast to electrical treeing, which results from internalelectrical discharges that decompose the dielectric, water treeing isthe deterioration of a solid dielectric material, which issimultaneously exposed to liquid or vapor and an electric field. Buriedpower cables are especially vulnerable to water treeing. Water treesinitiate from sites of high electrical stress such as rough interfaces,protruding conductive points, voids, or imbedded contaminants, but atlower voltages than that required for electrical trees. In contrast toelectrical trees, water trees have the following distinguishingcharacteristics; (a) the presence of water is essential for theirgrowth; (b) no partial discharge is normally detected during theirinitiation; (c) they can grow for years before reaching a size that maycontribute to a breakdown; (d) although slow growing, they are initiatedand grow in much lower electrical fields than those required for thedevelopment of electrical trees.

Electrical insulation applications are generally divided into lowvoltage insulation (less than 1 K volts), medium voltage insulation(ranging from 1 K volts to 65 K volts), and high voltage insulation(above 65 K volts). In low to medium voltage applications, for example,electrical cables and applications in the automotive industry,electrical treeing is generally not a pervasive problem and is far lesscommon than water treeing, which frequently is a problem. Formedium-voltage applications, the most common polymeric insulators aremade from either polyethylene homopolymers or ethylene-propyleneelastomers, otherwise known as ethylene- propylene-rubber (EPR) orethylene-propylene-diene ter-polymer (EPDM).

Polyethylene is generally used neat (without a filler) as an electricalinsulation material. Polyethylenes have very good dielectric properties,especially dielectric constants and power factors. The dielectricconstant of polyethylene is in the range of about 2.2 to 2.3. The powerfactor, which is a function of electrical energy dissipated and lost andshould be as low as possible, is around 0.0002 at room temperature, avery desirable value. The mechanical properties of polyethylene polymersare also adequate for utilization in many applications as medium-voltageinsulation, although they are prone to deformation at high temperatures.However, polyethylene homopolymers are very prone to water treeing,especially toward the upper end of the medium-voltage range.

There have been attempts to make polyethylene-based polymers that wouldhave long-term electrical stability. For example, when dicumyl peroxideis used as a crosslinking agent for polyethylene, the peroxide residuefunctions as a tree inhibitor for some time after curing. However, theseresidues are eventually lost at most temperatures where electrical powercable is used. U.S. Pat. No. 4,144,202 issued Mar. 13, 1979 to Ashcraft,et al. discloses the incorporation into polyethylenes of at least oneepoxy containing organo-silane as a treeing inhibitor. However, a needstill exists for a polymeric insulator having improved treeingresistance over such silane containing polyethylenes.

Unlike polyethylene, which can be utilized neat, the other commonmedium- voltage insulator, EPR, typically contains a high level offiller in order to improve thermal properties and reduce cost. Whenutilized as a medium-voltage insulator, EPR will generally contain about20 to about 50 weight percent filler, most likely calcined clay, and ispreferably crosslinked with peroxides. The presence of the filler givesEPR a high resistance against the propagation of trees. EPR also hasmechanical properties, which are superior to polyethylene at elevatedtemperatures.

Unfortunately, while the fillers utilized in EPR may help preventtreeing, the filled EPR will generally have poorer dielectricproperties, i.e. a poorer dielectric constant and a poor power factor.The dielectric constant of filled EPR is in the range of about 2.3 toabout 2.8. Its power factor is on the order of about 0.002 to about0.005 at room temperature, which is approximately an order of magnitudeworse than polyethylene.

Thus, both polyethylenes and EPR have serious limitations as anelectrical insulator in cable applications. Although polyethylenepolymers have good electric properties, they have poor water treeresistance. While filled EPR has good treeing resistance and goodmechanical properties, it has dielectric properties inferior topolyethylene polymers.

Power factor increases with temperature. In addition it may continue toincrease with time at high temperatures. Underwriters Labs MV105 ratedcables must be able to survive 21 days at an emergency circuit overloadtemperature of 140° C. Filled EPR insulations are usually used in theseapplications.

Another class of polymers is described in EP-A-0 341 644 published Nov.15, 1989. This reference describes linear polyethylenes produced by atraditional Ziegler-Natta catalyst systems. They generally have a broadmolecular weight distribution similar to linear low-density polyethyleneand at low enough densities can show better tree retardancy. However,these linear-type polymers in the wire and cable industry have poor meltflow characteristics and poor processability. In order to achieve a goodmix in an extruder, linear polymers must be processed at a temperatureat which the peroxides present in the polymer prematurely crosslink thepolymers, a phenomenon commonly referred to as scorch. If the processingtemperature is held low enough to avoid scorch, incomplete meltingoccurs because of the higher melting species in linear polymers having abroad molecular weight distribution. This phenomenon results in poormixing, surging extruder pressures, and other poor results.

Newer metallocene polyethylene co-polymers are more flexible and havebeen proposed for use as cable insulation but they also have generallypoorer thermal stability, and may deform when exposed to high heat. Theyalso suffer from higher electrical loss with AC current which may bemeasured in the form of a dissipation factor called tan delta.

1,2-dihydro-2-2-4 trimethylquinolines or “TMQs” are the universallypreferred antioxidants for filled LV, MV or HV cable insulations becauseof their good thermal degradation protection, low interference with theperoxide cure systems widely used and low cost. TMQs are not used inpolyethylene insulation because of their staining nature.

Hindered amine light stabilizers or “HALS” are primarily used in clearplastic film, sheets or coatings to prevent degradation by light. HALSare used in unfilled polyethylene insulations. They are thought toprevent degradation caused by light emitted by tiny electricaldischarges. U.S. Pat. No. 5,719,218 discloses an optically transparentpolyethylene insulation formulation with a HAL where it is stated thatthe HALS are useful for the prevention of degradation of the insulationby water trees.

EPDM type insulations have excellent resistance to water trees and havebeen used for over 30 years in AC cable insulations exposed to wetenvironments. They are also proven to perform in high temperatureservice in urban power networks. Filled insulations are opaque so theydo not suffer from degradation caused by light emitted by tinyelectrical discharges.

Metallocene polymers have shown much higher resistance to water treesthan polyethylene but are not widely used as medium or high voltage ACcable insulation due to their higher AC loss and generally poorerthermal degradation resistance and higher cost than polyethylene.Metallocene polymers do have good acceptance of fillers and can be usedfor flexible, low temperature, low voltage or DC insulations. Unfilledpolyethylene compositions such as those disclosed in U.S. Pat. No.5,719,218 are prone to staining when certain additives such as TMQ arepresent, as discussed above. WO 02/29829 uses the unfilled polyethylenecomposition disclosed in U.S. Pat. No. 5,719,218 in an unfilledstrippable insulation composition which contains a tetramethylpiperidinehindered amine light stabilizer additive.

Therefore, a need exists in the electrical cable industry for anadditive system that improves the performance of metallocene polymers asa filled insulation composition.

SUMMARY OF THE INVENTION

The invention provides an additive system that improves the performanceof metallocene polymers when used as a filled insulation composition.

Specifically, the invention provides an insulation composition forelectric cable comprising; (a) a base polymer comprising at least onemetallocene polymer; (b) a filler; and (c) an additive comprising ablend of; (i) an amine antioxidant, and (ii) a hindered amine lightstabilizer or stabilizers, or 2,5-Di(tert-amyl)hydroquinone (TAHQ), ormixtures of said stabilizer(s) and TAHQ.

In another embodiment of the invention, the insulation composition basepolymer -15 further comprises at least one non-metallocene polymer.

In embodiments of the invention, the base polymer may comprise 20% to99% by weight metallocene polymer and 1% to 80% by weightnon-metallocene polymer, and the additive may be from about 0.25% toabout 2.5% by weight of said insulation composition, preferably fromabout 0.5% to about 1.5% by weight of said insulation composition. 20

DETAILED DESCRIPTION OF THE INVENTION

The invention particularly relates to polymeric compositions utilizingpolyolefins, which compositions have a unique combination of goodmechanical properties, good dielectric properties, and good watertreeing resistance, as well as a lower melt temperature for improvedprocessability when the compositions include peroxide-containingcompounds. The products are extremely useful as insulation compositionsfor electric power cables.

The polymers utilized in the protective jacketing, insulating,conducting or semiconducting layers of the inventive cables of theinvention may be made by any suitable process which allows for the yieldof the desired polymer with the desired physical strength properties,electrical properties, tree retardancy, and melt temperature forprocessability.

The base polymer in accordance with the invention comprises at least onemetallocene polymer, and also may include, if desired, non-metallocenepolymers.

Metallocene polymers are produced using a class of highly active olefincatalysts known as metallocenes, which for the purposes of thisapplication are generally defined to contain one or morecyclopentadienyl moiety. The manufacture of metallocene polymers isdescribed in U.S. Pat. No. 6,270,856 to Hendewerk, et al, the disclosureof which is incorporated by reference in its entirety.

Metallocenes are well known especially in the preparation ofpolyethylene and copolyethylene-alpha-olefins. These catalysts,particularly those based on group IV transition metals, zirconium,titanium and hafnium, show extremely high activity in ethylenepolymerization. Various forms of the catalyst system of the metallocenetype may be used for polymerization to prepare the polymers used in thisinvention, including but not limited to those of the homogeneous,supported catalyst type, wherein the catalyst and cocatalyst aretogether supported or reacted together onto an inert support forpolymerization by a gas phase process, high pressure process, or aslurry, solution polymerization process. The metallocene catalysts arealso highly flexible in that, by manipulation of the catalystcomposition and reaction conditions, they can be made to providepolyolefins with controllable molecular weights from as low as about 200(useful in applications such as lube-oil additives) to about 1 millionor higher, as for example in ultra-high molecular weight linearpolyethylene. At the same time, the MWD of the polymers can becontrolled from extremely narrow (as in a polydispersity of about 2), tobroad (as in a polydispersity of about 8).

Exemplary of the development of these metallocene catalysts for thepolymerization of ethylene are U.S. Pat. No. 4,937,299 and EP-A-0 129368 to Ewen, et al., U.S. Pat. No. 4,808,561 to Welborn, Jr., and U.S.Pat. No. 4,814,310 to Chang, which are all hereby are fully incorporatedby reference. Among other things, Ewen, et al. teaches that thestructure of the metallocene catalyst includes an alumoxane, formed whenwater reacts with trialkyl aluminum. The alumoxane complexes with themetallocene compound to form the catalyst. Welborn, Jr. teaches a methodof polymerization of ethylene with alpha-olefins and/or diolefins. Changteaches a method of making a metallocene alumoxane catalyst systemutilizing the absorbed water in a silica gel catalyst support. Specificmethods for making ethylene/alpha- olefin copolymers, andethylene/alpha-olefin/diene terpolymers are taught in U.S. Pat. No.4,871,705 (issued Oct. 3, 1989) and U.S. Pat. No. 5,001,205 (issued Mar.19, 1991) to Hoel, et al., and in EP- A-0 347 129 published Apr. 8,1992, respectively, all of which are hereby fully incorporated byreference.

Other cocatalysts may be used with metallocenes, such astrialkylaluminum compounds or ionizing ionic activators, such astri(n-butyl)ammonium tetra(pentafluorophenyl) boron, which ionize theneutral metallocene compound. Such ionizing compounds may contain anactive proton or some other cation such as carbonium, which ionizing themetallocene on contact, forms a metallocene cation associated with (butnot coordinated or only loosely coordinated with) the remaining ion ofthe ionizing ionic compound. Such compounds are described in EP-A-0 277003 and EP-A-0 277 004, both published Aug. 3, 1988, and are hereinfully incorporated by reference. Also, the polymers useful in thisinvention can be a metallocene catalyst component that is amonocylopentadienyl compound, which is activated by either an alumoxaneor an ionic activator to form an active polymerization catalyst system.Catalyst systems of this type are shown by PCT International PublicationWO92/00333, published Jan. 9, 1992, U.S. Pat. Nos. 5,096,867 and5,055,438, EP-A-0 420 436 and WO91/04257 all of which are fullyincorporated herein by reference. The catalyst systems described abovemay be optionally prepolymerized or used in conjunction with an additivecomponent to enhance catalytic productivity.

As previously stated, metallocene catalysts are particularly attractivein making tailored ultra-uniform and super-random specialty copolymers.For example, if a lower density copolymer is being made with ametallocene catalyst such as very low density polyethylene, (VLDPE), anultra-uniform and super random copolymerization will occur, ascontrasted to the polymer produced by copolymerization using aconventional Ziegler-Natta catalyst. In view of the ongoing need forelectrical cables having improved mechanical and dielectric propertiesand improved water treeing resistance, as well as the need to processthese materials at temperatures low enough to allow scorch freeprocessing, it would be desirable to provide products utilizing the highquality characteristics of polyolefins prepared with metallocenecatalysts.

The base polymer utilized in the insulation composition for electriccable in accordance with the invention may also be selected from thegroup of polymers consisting of ethylene polymerized with at least onecomonomer selected from the group consisting of C₃ to C₂₀ alpha-olefinsand C₃ to C₂₀ polyenes. Generally, the alpha-olefins suitable for use inthe invention contain in the range of about 3 to about 20 carbon atoms.Preferably, the alpha-olefins contain in the range of about 3 to about16 carbon atoms, most preferably in the range of about 3 to about 8carbon atoms. Illustrative non-limiting examples of such alpha-olefinsare propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-dodecene.

Preferably, the polymers utilized in the cables of the invention areeither ethylene/alpha-olefin copolymers or ethylene/alpha-olefin/dieneterpolymers. The polyene utilized in the invention generally has about 3to about 20 carbon atoms. Preferably, the polyene has in the range ofabout 4 to about 20 carbon atoms, most preferably in the range of about4 to about 15 carbon atoms. Preferably, the polyene is a diene, whichcan be a straight chain, branched chain, or cyclic hydrocarbon diene.Most preferably, the diene is a non conjugated diene. Examples ofsuitable dienes are straight chain acyclic dienes such as:1,3-butadiene, 1,4-hexadiene and 1,6-octadiene; branched chain acyclicdienes such as: 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,3,7-dimethyl-1,7-octadiene and mixed isomers of dihydro myricene anddihydroocinene; single ring alicyclic dienes such as:1,3-cyclopentadiene, 1,4-cylcohexadiene, 1,5-cyclooctadiene and1,5-cyclododecadiene; and multi-ring alicyclic fused and bridged ringdienes such as: tetrahydroindene, methyl tetrahydroindene,dicylcopentadiene, bicyclo-(2,2,1)-hepta-2-5-diene; alkenyl, alkylidene,cycloalkenyl and cycloalkylidene norbornenes such as5-methylene-2morbomene (MNB), 5-propenyl-2-norbornene,5-isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene,5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and norbornene. Ofthe dienes typically used to prepare EPR's, the particularly preferreddienes are 1,4-hexadiene, 5-ethylidene-2-norbornene,5-vinyllidene-2-norbornene, 5-methylene-2-norbornene anddicyclopentadiene. The especially preferred dienes are5-ethylidene-2-norbornene and 1,4-hexadiene.

In preferred embodiments of the invention, the base polymer comprisesmetallocene EP which is an EPR or EPDM polymer prepared with metallocenecatalysts. In embodiments of the invention, the base polymer may bemetallocene EP alone, metallocene EP and at least one other metallocenepolymer, or metallocene EP and at least one non-metallocene polymer asdescribed below.

As an additional polymer in the base polymer composition, anon-metallocene base polymer may be used having the structural formulaof any of the polyolefins or polyolefin copolymers described above.Ethylene-propylene rubber (EPR), polyethylene, polypropylene or ethylenevinyl acetates having a range of vinyl acetate content of from about 10%to about 40% may all be used in combination with the metallocenepolymers in the base polymer.

In embodiments of the invention, the insulation composition base polymercomprises 20% to 99% by weight metallocene polymer or polymers and 1% to80% by weight non-metallocene polymer or polymers. The additive ispresent in amounts from about 0.25% to about 2.5% by weight of saidcomposition, preferably from about 0.5% to about 1.5% by weight of saidcomposition. In preferred embodiments, the additive has a weight/weightratio of HALS/TMQ of from about 90/10 to about 10/90, more preferably aweight/weight ratio of HALS/TMQ of from about 75/25 to about 25/75.

As described above, the additive in accordance with the inventioncomprises a blend of; (i) an amine antioxidant, and (ii) a hinderedamine light stabilizer, or 2,5-Di(tert- amyl)hydroquinone (TAHQ) ormixtures of said stabilizer and TAHQ. In further embodiments of theinvention, the additive in accordance with the invention comprises atleast two hindered amine light stabilizers. In further embodiments ofthe invention, the additive in accordance with the invention comprisesat least two hindered amine light stabilizers and TAHQ.

Any suitable hindered amine light stabilizer may be used in accordancewith the invention, for example, Bis (2,2,6,6-tetramethyl-4-piperidyl)sebaceate (tinuvin 770); Bis (1,2,2,6,6-tetramethyl-4-piperidyl)sebaceate +methyl 1,2,2,6,6-tetramethyl-4-piperidyl sebaceate (tinuvin765); 1,6-Hexanediamine, N,N′-Bis (2,2,6,6-tetramethyl-4-piperidyl)polymer with 2,4,6 trichloro-1,3,5-triazine, reaction products withN-butyl 2,2,6,6-tetramethyl-4-piperidinamine (Chimassorb 2020);Decanedioic acid, Bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidyl)ester, reaction productswith 1, 1-dimethylethylhydroperoxide and octane (Tinuvin 123); Triazinederivatives (tinuvin NOR 371); Butanedioic acid, dimethylester 4hydroxy-2,2,6,6-tetramethyl-piperidine ethanol (Tinuvin 622),1,3,5-Triazine-2,4,6-triamine,N,N′″-[1,2-ethane-diyl-bis[[[4,6-bis-[butyl(1,2,2,6,6pentamethyl-4-piperdinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]bis [N′,N″-dibutyl-N′,N″ bis(2,2,6,6-tetramethyl-4-piperidyl)(Chimassorb 119). Chimassorb 944 LD and Tinuvin 622 LD are preferredhindered amine light stabilizers.

Any suitable amine antioxidant may be used in accordance with theinvention, for example, 1,2-dihydro-2-2-4, trimethylquinoline (AgeriteMA, Agerite D, Flectol TMQ), octylated diphenylamine (Agerite Stelite),diphenyl-p-phenylene-diamine (Agerite DPPD),4,4′-di(1,1-dimethylbenzyl)-diphenylamine (Naugard 445),ethoxy-1,2-dihydro-2-2-4 trimethylquinoline (Santaflex AW),p,p′-dioctyldiphenylamine (Vanox 12), 2-tert- butylhydroquinone (EastmanTenoxTBHQ), N-(1,3-dimethyl butyl)-N′-phenyl-p-phenylene diamine(Vulcanox 4020), N-phenyl-N′isopropyl-p-phenylene diamine(Vulcanox4010), p- phenylene diamine (Wingstay 100). 1,2-dihydro-2-2-4,Trimethylquinoline is a preferred amine antioxidant.

The insulating composition the invention is filled. An illustrativeexample of a suitable filler is clay, talc (aluminum silicate ormagnesium silicate), magnesium aluminum silicate, magnesium calciumsilicate, calcium carbonate, magnesium calcium carbonate, silica, ATH,magnesium hydroxide, sodium borate, calcium borate, kaolin clay, glassfibers, glass particles, or mixtures thereof. In accordance with theinvention, the weight percent range for fillers is from about 10 percentto about 60 percent, preferably from about 20 to about 50 weight percentfiller.

Other additives commonly employed in the polyolefin compositionsutilized in the invention can include, for example, crosslinking agents,antioxidants, processing aids, pigments, dyes, colorants, metaldeactivators, oil extenders, stabilizers, and lubricants.

All of the components of the compositions utilized in the invention areusually blended or compounded together prior to their introduction intoan extrusion device from which they are to be extruded onto anelectrical conductor. The polymer and the other additives and fillersmay be blended together by any of the techniques used in the art toblend and compound such mixtures to homogeneous masses. For instance,the components may be fluxed on a variety of apparatus includingmulti-roll mills, screw mills, continuous mixers, compounding extrudersand Banbury mixers.

After the various components of the composition are uniformly admixedand blended together, they are further processed to fabricate the cablesof the invention. Prior art methods for fabricating polymer insulatedcable and wire are well known, and fabrication of the cable of theinvention may generally be accomplished any of the various extrusionmethods.

In a typical extrusion method, an optionally heated conducting core tobe coated is pulled through a heated extrusion die, generally across-head die, in which a layer of melted polymer is applied to theconducting core. Upon exiting the die, the conducting core with theapplied polymer layer is passed through a heated vulcanizing section, orcontinuous vulcanizing section and then a cooling section, generally anelongated cooling bath, to cool. Multiple polymer layers may be appliedby consecutive extrusion steps in which an additional layer is added ineach step, or with the proper type of die, multiple polymer layers maybe applied simultaneously.

The conductor of the invention may generally comprise any suitableelectrically conducting material, although generally electricallyconducting metals are utilized. Preferably, the metals utilized arecopper or aluminum. In power transmission, aluminum conductor/steelreinforcement (ACSR) cable, aluminum conductor/aluminum reinforcement(ACAR) cable, or aluminum cable is generally preferred.

EXAMPLES

The samples in the tables were mixed in a 3.17 liter banbury at 70-75RPM. Batch size was 2300g -2500g. Half of the polymer was added first.After the polymer fluxed, the clays, antioxidants, and pigments wereadded. The remaining polymer(s ) were added next. After material fluxed,the wax was added. The material was removed from the banbury when thetemperature reached 275° F. Total mix time was 4-8 minutes.

For the 2^(nd) pass Banbury the mix speed was at 50-60 RPM. Half of thematerial from the 1^(st) pass was added, and after it fluxed theperoxide was added. Then the remainder of the material was added. Thematerial was removed from the banbury when the temperature reached 230°F. Total mix time was 1.5-5 minutes.

Samples were pressed to 45 mill cured slab at 350 degrees F. for 20minutes.

Samples were tested for Dissipation factor with a Tettex 2818dissipation factor test set connected to a Tettex 2914 precision solidsdielectric cell as follows

-   -   1. Degas Slabs overnight in Vacuum Oven @ 70° C.    -   2. Measure Unaged SIC/TD @ 130° C.    -   3. Age slabs 14 days @ 140° C.    -   4. Measure Aged SIC/TD @ 130° C.

Tensile properties were tested according to ASTM D412

Mh was tested on an Alfa Technologies MDR 2000 with Y2 degree arc andscorch was tested on an Alfa Technologies Mooney 2000.

The following materials were used:

Antioxidants

-   -   Agerite TMQ/, Polymerized 1,2-dihydro-2,2,4-trimethylquinoline,        Antioxidant, R.T. Vanderbilt Company, Inc., Norwalk, Conn.    -   Irganox 1035, Thiodiethylene        bis(3,5-di-(tert)-butyl-4-hydroxyhydrocinnamate, Antioxidant,        Ciba Specialty Chemicals Corp., Tarrytown, N.Y.    -   Naugard 76,        Octadecyl,3,5,-di-tert-butyl-4-hydroxyhydrocinnamate,        Antioxidant, Uniroyal Chemical Company, Inc., Middlebury, Conn.    -   Vanox AM, 2-Propanone, Antioxidant, R.T. Vanderbilt Company,        Inc., Norwalk, Conn.    -   Vanox DSTDP, Distearyl thiodipropionate, Secondary Antioxidant,        R.T. Vanderbilt Company, Inc., Norwalk, Conn.    -   Vanox ZMTI, 2H-Benzimidazole-2-thione, 1,3-dihydro-4(or        5)-methyl-, Antioxidant, R.T. Vanderbilt Company, Inc., Norwalk,        Conn.

TAHQ

-   -   Santovar TAHQ, 2,5-Di(tert-amyl)hydroquinone, A, Flexsys        Amerikca L.P., Akron, Ohio

HALS

-   -   Chimassorb 81, 2-Hydroxy-4-n-octoxybenzophenone, Ciba Specialty        Chemicals Corp., Tarrytown, N.Y.    -   Chimassorb 944 LD,        Poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl],        Ciba Specialty Chemicals Corp., Tarrytown, N.Y.    -   Tinuvin 622 LD, Dimethyl succinate polymer        w/4-hydroxy-2,2,6,6,-tertramethyl-1-piperidineethanol, Ciba        Specialty Chemicals Corp., Tarrytown, N.Y.    -   Tinuvin 783 FDL, 50% by wt Tinuvin 622 and 50% by wt Chimassorb        944, Light Stabilizer, Ciba Specialty Chemicals Corp.,        Tarrytown, N.Y.

Polymers

-   -   Vistalon, Ethylene Propylene Diene Rubber, Polymer, 0.86 g/ml,        ExxonMobil Chemical Company, Houston, Tex.    -   Engage 8200, Copolymer of Ethylene and Octene-1, Polymer, 0.87        g/ml, Dupont Dow Elastomers L. L. C., Wilmington, Del.    -   Exact 4006, Ethylene-Olefin Copolymer, Polymer, 0.9 g/ml,        ExxonMobil Chemical Company, Houston, Tex.    -   LDPE, Low-density Polyethylene, Polymer, 0.92 g/ml, Equistar        Chemicals, LP, Houston, Tex.

Filler

-   -   Polyfil, Chemically Treated Anhydrous Aluminum Silicate, Filler,        Huber Engineered Materials, Macon, Ga.

Minor Ingredients

-   -   Red Lead, Lead(II,IV)-oxide, Activator, Hammond Lead Products,        Hammond, Indiana    -   Recco 140, Paraffin Wax, Processing Aid, R.E. Carroll Inc.,        Trenton, N.J.    -   (Silane) A172-50G, 50% Vinyl-tris(2-methoxyethoxy) silane in a        50% elastomeric (EPDM), Coupling Agent, UA Rubber Specialty        Chemical Sdn. Bhd., Bukit Mertajaam. Malaysia    -   Zinc Oxide, Activator, U.S. Zinc Corp., Chicago, Ill.

DI-Cup, Dicumyl Peroxide, Cross-Linker, Hercules Incorporated,Wilmington, Del. COMPARATIVE EXAMPLES A B C D E F Vistalon EPDM 51Engage 8200 51 51 51 51 51 Exact 4006 LPDE 10 10 10 10 10 10 A172treated day filler 28.9 28.9 28.9 28.9 28.9 28.9 Paraffin Wax 2.8 2.82.8 2.8 2.8 2.8 red lead 3 3 3 3 3 3 (A172) silane 0.5 0.5 0.5 0.5 0.50.5 Zinc oxide 2.8 2.8 2.8 2.8 2.8 2.8 Agerite TMQ 1 1 0.75 DSTDP .25.25 naugard 76 1 vanox ZMTI Irganox 1035 0.75 Chimassorb 944 Tinuvin783FDL Tinuvin 622LD Vanox ZMTI 0.25 Santovar TAHQ Vanox AM 0.75 Dicup1.5 1.5 1.5 1.5 1.5 1.5 TOTAL 101.5 101.5 101.5 101.5 101.5 101.5 TanDelta at 130 C % 1.3 3.6 3.6 NA NA 3.8 Tan Delta 130C % aged 14d 140C1.2 10 11.3 12 Tan Delta 130C % aged 21d 140C 1.1 8.7 10.5 12.4 MDRreports min. to min. 6 Min @ 400° F. MH 14.6 6.6 6.54 10.35 10.2 7.65 ML0.83 0.22 0.21 0.23 0.23 0.2 MOONEY SCORCH 130° C./30 min SCORCH TIME @Ts 5 30 30 30 30 30 40 INITIAL TENSILE (PSI) 1791 1812 1760 1903 19091850 % ELONGATION 315 471 525 490 477 515 AGED 21 Days 140° C. % TENSRETAINED 91 91 92 0 4 88 % ELONG RETAINED 92 105 98 0 1 94 AGED 21 Days150° C. % TENS RETAINED 67 32 71 0 0 58 % ELONG RETAINED 70 7 67 0 0 41

Invention Examples 1-8 According to Invention and Comparative Example G1 2 3 4 5 G 6 7 8 Vistalon EPDM Engage 8200 51 51 51 51 51 Exact 4006 5151 51 51 LPDE 10 10 10 10 10 10 10 10 10 A172 treated clay filler 28.928.9 28.9 28.9 28.9 28.9 28.9 28.9 28.9 Paraffin Wax 2.8 2.8 2.8 2.8 2.82.8 2.8 2.8 2.8 red lead 3 3 3 3 3 3 3 3 3 (A172) silane 0.5 0.5 0.5 0.50.5 0.5 0.5 0.5 0.5 Zinc oxide 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8Agerite TMQ 0.5 0.5 0.75 0.75 1 0.75 0.7 DSTDP naugard 76 vanox ZMTIIrganox 1035 Chimassorb 944 1 0.25 1 0.3 Tinuvin 783FDL 0.5 Tinuvin622LD 0.5 Vanox ZMTI Santovar TAHQ 0.25 0.25 Vanox AM Dicup 1.5 1.5 1.51.5 1.5 1.5 1.5 1.5 1.5 TOTAL 101.5 101.5 101.5 101.5 101.5 101.5 101.5101.5 101.5 Tan Delta at 130 C % 2.5 1.9 2.27 3.7 3 1.25 1.34 1.29 1.3Tan Delta 130C % aged 14d 140C 4.7 4.6 6.9 9.36 10.5 1.3 0.93 0.92 0.92Tan Delta 130C % aged 21d 140C 5.1 5.5 6.6 9.5 12.9 1.3 0.9 0.85 0.84MDR reports min. to min. MH 6.77 9.57 8.85 6.64 7.05 10.7 11.26 12.8 11ML 0.24 0.3 0.27 0.2 0.17 0.13 0.11 0.16 0.14 MOONEY SCORCH 130° C./30min SCORCH TIME @ Ts 5 20.4 28.8 25 30 40 28.5 30 22 30 INITIAL TENSILE(PSI) 1807 1883 1876 1747 1834 1995 1987 2121 2005 % ELONGATION 555 492493 510 521 332 471 532 501 AGED 21 Days 140° C. % TENS RETAINED 88 9394 94 96 89 92 77 92 % ELONG RETAINED 81 103 98 99 99 97 96 72 99 AGED21 Days 150° C. % TENS RETAINED 53 84 79 81 76 70.9 38.7 43 68 % ELONGRETAINED 40 79 86 85 83 70 14 32 93

The antioxidant systems of the invention provide good protection againstthermal degradation, better cure state and reduced dissipation factorafter prolonged heat exposure in filled metallocene AC insulations.

In particular, the demonstrated additive systems comprising TAHQ improveheat aging and scorch properties. The demonstrated additive systemscomprising one or more HALS improve Tan Delta, usually improve heataging properties and sometimes improve scorch properties. It is expectedthat additive systems comprising both TAHQ and one or more HALS wouldobtain at least the individual benefits of both.

Lettered examples are comparative examples and numbered examples areexamples in accordance with the invention.

Comparative Example A shows the good thermal and electrical propertiesof a traditional Zeigler-Natta EPR rubber formulation. ComparativeExample B shows the poor performance of a metallocene polymer in thesame formulation. Comparative Examples C - F show poor performance withother known antioxidant systems. Embodiments of the invention as shownin Examples 1 to 3 show the greatly improved thermal properties anddramatically improved dissipation factor after aging. Embodiments of theinvention as shown in Examples 4 and 5 do not show improved electricalproperties but do show the greatly improved thermal properties. In fact,Embodiments of the invention as shown in Examples 2 to 5 show superiorthermal properties to Example A. Embodiments of the invention as shownin Examples 2, 3 and S show an increased state of cure as compared toExample B.

Dissipation factors were generally higher because the Engage 8200polymer was not electrical grade.

Comparative Example G shows a different metallocene polymer that hadbetter thermal and electrical properties but still showed electricalimprovement with the antioxidant systems of the invention. Embodimentsof the invention as shown in Example 8 show improved thermal propertiesat 150 C and Embodiments of the invention as shown in Examples 6, 7, and8 show higher cure state.

While the present invention has been described and illustrated byreference to particular embodiments thereof, it will be appreciated bythose of ordinary skill in the art that the invention lends itself tovariations not necessarily illustrated herein.

For this reason, then, reference should be made solely to the appendedclaims for the purposes of determining the true scope of this invention.

1-20. (canceled)
 21. An insulation composition for electric cablecomprising: (a) a base polymer comprising metallocene ethylene-butenepolymer; (b) a filler; and (c) an additive comprising a blend of; (i) anamine antioxidant, and (ii) a hindered amine light stabilizer.
 22. Aninsulation composition according to claim 21 wherein said base polymerfurther comprises at least one non-metallocene polymer.
 23. Aninsulation composition according to claim 22 wherein said base polymercomprises 20% to 99% by weight metallocene polymer and 1% to 80% byweight non-metallocene polymer.
 24. An insulation composition accordingto claim 21 wherein said additive is from about 0.25% to about 2.5% byweight of said composition.
 25. An insulation composition according toclaim 21 wherein said additive is from about 0.5% to about 1.5% byweight of said composition.